Transition metal complexes with pyrazole-based ligands, Part 29: Reactions of zinc(II) and mercury(II) thiocyanate with 4-acetyl-3-amino-5-methylpyrazole

Abstract

The work is concerned with the crystal and molecular structures of zinc(II) and mercury(II) complexes with 4-acetyl-3-amino-5-methyl--pyrazole (aamp) of the coordination formulae [Zn(NCS) 2 (aamp) 2 ] and (Haamp) 2 [Hg(SCN) 4 ]. The zinc(II) complex was obtained by the reaction of a warm methanolic solution of aamp with a mixture of zinc(II) nitrate and ammonium thiocyanate, whereas the mercury(II) complex was prepared by the reaction of a warm ethanolic solution of aamp and a warm, slightly acidified aqueous solution of [Hg(SCN) 4 ] 2-. Both complexes have a tetrahedral geometry, which in the case of zinc complex is formed by monodentate coordination of two aamp molecules and two isothiocyanate groups. The Zn(II) and Hg(II) atoms have significantly deformed coordination geometry. In both crystal structures the pyrazole derivative has a planar form, probably stabilized by an intramolecular N-H⋅⋅⋅O hydrogen bond. Apart from the X-ray structural analysis, the isolated complexes were characterized by elemental analysis, IR spectroscopy, conductometric measurements and thermal analysis. COMPLEXES OF Zn(II) AND Hg(II) WITH 4-ACETYL-3-AMINO-5-METHYLPYRAZOLE 1261 X-Ray experiments and crystal structure determinationSingle-crystal X-ray diffraction data for (Haamp) 2 [Hg(SCN) 4 ] were collected on an Enraf-Nonius CAD-4 diffractometer 18 using MoKα radiation (λ = 0.71069 Å) and ω/2θ scans in the 2θ range from 1.67 to 29.96°. The cell constants and an orientation matrix for data collection, obtained from 24 centered reflections in the range 12.10-16.82°, corresponded to a monoclinic cell, the dimensions of which are given in Table I. The data were corrected for Lorentz and polarization effects. 19 A Gaussian-type absorption correction 20-22 based on the crystal morphology was applied (T min = 0.217; T max = 0.354).

Synthesis and crystal structure of Cu(II) and Co(II) complexes with 1,3-dimethyl-pyrazole-5-carboxylic acid ligand

“…The wide biological activity of this class of compounds (anticancer, antimicrobial, antiviral, anti-inflammatory and others) is described in several reviews. 1 Apart from the investigation of the biological activity of pyrazole derivatives, they have been extensively used as ligands or synthons in coordination chemistry 2 and crystal engineering including the metal organic frameworks. 3 The most of these valuable functions of pyrazole ligands originate in their various bonding modes to metal ions that can be further influenced and rationally designed by the attachment of substituents with additional coordination sites.…”

Synthesis and characterization of some pyrazole derivatives and their reactions with transition metals

“…Molekulska struktura [Zn(NCS)2(aamp)2] (5) 153 Slika 5.18. Molekulska struktura (Haamp)2[Hg(SCN)4] (6)153 …”